Field of the Invention
The present invention relates to a grass mower machine including a mower deck attached to a machine body via a lift mechanism to be adjustable in its ground height and an electric motor for providing power to a rotation shaft configured to rotate a cutter blade disposed inside the mower deck.
Description of the Related Art
A vehicle disclosed in the specification of the U.S. Pat. No. 8,042,322 includes a mower deck, a rotation shaft supported to the mower deck side by side and extending in a vertical direction, and a cutter blade fixed to a lower end of this rotation shaft. On an upper wall face of the mower deck, an electric motor is disposed with lateral orientation between two rotation shafts. An output shaft of the electric motor extends horizontally from opposed ends of the electric motor toward the respective rotation shafts. As the output shaft and the rotation shafts are connected via a bevel gear, so that with drive of the electric motor, the cutter blade is rotated. If this arrangement is used in a mower having a mower deck that is attached to a machine body via a lift mechanism to be adjustable in its ground height, a space above the top wall of the mower deck is largely occupied by the electric motor and the bevel gear. Thus, the gap between the electric motor, the bevel gear and the machine body is small, which makes it difficult to secure a sufficient ground height for the mower deck. If the height of the machine body is increased in order to secure a sufficient ground height (lift stroke) for the mower deck, this will invite inconvenience of elevation of the center of gravity of the machine body.
A lawn tractor (a grass mower machine) disclosed in the specification of the U.S. Pat. No. 8,191,343 includes a mower deck mounting three cutter blades side by side. Of the three cutter blades, the center cutter blade is attached to a lower end of a center rotation shaft whose upper end is coupled to an output shaft of an electric motor. The left rotation shaft attached with the left cutter blade and the right rotation shaft attached with the right cutter blade, of the three cutter blades, receive power from the center rotation shaft via a belt transmission. The electric motor is disposed at the highest position of the mower deck. A controller for supplying electric power to the electric motor is disposed in a region surrounded by the center rotation shaft, the left rotation shaft and the right rotation shaft on the top wall of the mower deck, and its ground height is lower than that of the electric motor. In this lawn tractor too, the electric motor is disposed at an upper end of the center rotation shaft, so the gap between the electric motor and the machine body is small, which makes it difficult to secure a sufficient ground height for the mower deck.
An electric grass mower machine disclosed in the specification of the U.S. Pat. No. 8,572,939 includes a mower deck mounting three cutter blades side by side. Electric motors are disposed at upper ends of rotation shafts of all the cutter blades, and power supply to the respective electric motor is done by a power supply system comprised of an inverter and a battery mounted on the machine body. With this electric grass mower machine too, the gaps between the electric motors and the machine body are small, which makes it difficult to secure a sufficient ground height for the mower deck.
With the conventional mower decks described above, cutter blade driving devices such as a gear mechanism, an electric motor, etc. having relatively large heights are disposed upwardly of a rotation shaft of the cutter blade. So, it was difficult to secure a sufficient lift stroke for the mower deck. For this reason, there is a need for a grass mower machine that makes it possible to secure a sufficient space between a mower deck and a machine body frame so as to secure a sufficient lift stroke for the mower deck.